MRI imaging of the knee at three tesla has allowed us to increase resolution and decrease scan time, with improved signal to noise.
The protocol consists of axial and coronal T2 weighted images along with sagittal and coronal proton density images. The T2 pulse sequence uses a Fast Spin Echo with echo train of 8 and has a TR of 3500 ms, TE of 85, receive bandwidth of 62.5 kHz, slice thickness of 4 mm, acquisition matrix of 512x256. The proton density sequence is a FSE with ETL 8, TE of 12 ms, BW 62.5, acquisition matrix of 512x256, with zero padding to 1024. The sequences have in plane resolution of 0.63 mm by 0.31 mm. This allows improved visualization of small meniscal tears and defects to cartilage. The high resolution brings some artifacts, chemical shift is more pronounced and the magic angle effect can make cartilage and sub cortical bone thickness appear to change depending on position. The effects were investigated with changes in bandwidth and frequency encoding direction. The effect of zero padding is also shown to increase visualization of bone trauma.